How do body cells fight back cancer?

What is a cancer?
Cancer cell are responsible for causing cancer. The cancer cells are body cells with excess, defective, uncontrollable multiplication or in similar words.. replication!! Well this is the problem! As our bodies immune system comprises of several different cells and proteins that generally recognize and attack
any molecules that are 'foreign' to our body, such as viruses or toxins. However, those cancer cells which develop and we then become aware that there is a problem, in that cancer is diagnosed, is due to those particular cancerous cells / tumours have developed mechanisms to avoid detection by the immune system. As a result, our immune system sees these cancerous cells as not being foreign and therefore fail to attack this cancerous growth.
Developing ones immune system, although it would not hurt, will do very little to get rid of these cancers which are not recognised by our bodies as being foreign. In fact some so called natural remedies such as high doses of Vitamin C, can in fact be extremely harmful and in some instances feed and promote the growth of certain cancers!
The answer is really to find a way to overcome some of tumour defence mechanisms and structure so that our immune system will have a chance to fight back (this is where some chemo and radiation tries to assist by destroying some of these cancerous cells). Doing so it may be possible for our bodies to cure themselves of cancer.